The invention discloses a Fe-Ni-P or Fe-Ni-P-RE amorphous alloy plating layer as well as plating liquid for electrodepositing and an electrodepositing method thereof, and belongs to the technical field of electrodepositing. With lactic acid and EDTA as complexing agents, and the other components of the plating liquid comprise ferrous salt, nickel salt, NaH2PO2, RECl3, H3BO3 and additives; by using the plating liquid using the lactic acid and the EDTA as the complexing agents, electrodepositing is carried out to obtain the Fe-Ni-P or Fe-Ni-P-RE amorphous alloy plating layer, wherein in the plating layer, the iron content is 5% to 90%, the nickel content is 5% to 90%, the sum of the iron and the nickel is 80% to 92%, the mass percentage of rare earth elements is 0 to 5%, and the balance is phosphorus. Through regulation of the process conditions such as the temperature of the plating liquid, the current density, a pH and the like, a Fe-Ni-P (RE) alloy film with excellent soft magnetic property can be successfully prepared and can be applied to the fields of micro-electronics and semiconductor functional devices.